Comparison of adsorption and passivation effects of inorganic and organic materials on cad-mium
In order to identify the adsorption effects of inorganic and organic materials on cadmium(Cd)in water and their passivation effects on soil Cd,twelve materials(fly ash,diatomite,coconut shell charcoal,medical stone,vermiculite powder,attapulgite powder,montmorillonite powder,humic acid,Chinese torreya shell,rice bran,poly-acrylamide,chitosan)were selected as test materials,electron microscopy observation,Cd solution adsorption tests,and soil passivation culture experiments were carried out.The evaluated parameters were surface properties,maxi-mum Cd adsorption capacity,and soil physiochemical properties.It was shown that the materials like humic acid,Chinese torreya shell,montmorillonite powder,vermiculite powder,attapulgite powder and diatomite had granular or layered structure and loose structure.All the test materials exhibited good adsorption properties for Cd in water.The maximum adsorption capacity of test materials decreased as humic acid(22.08 mg·g-1)＞Chinese torreya shell(21.99 mg·g-1)＞montmorillonite powder(16.24 mg·g-1)＞coconut shell charcoal(15.63 mg·g-1)＞vermicu-lite powder(13.81 mg·g-1)＞attapulgite powder(12.67 mg·g-1)＞fly ash(10.22 mg·g-1)＞polyacrylamide(9.20 mg·g-1)＞rice bran(8.72 mg·g-1)＞diatomite(5.90 mg·g-1)＞chitosan(4.79 mg·g-1)＞medical stone(3.65 mg·g-1).Except polyacrylamide and diatomite,application of these materials into soil(application rate of 1％)significantly(P＜0.05)reduced the content of available Cd in soil by 10.66％-32.68％.Among them,application of attapulgite powder and Chinese torreya shell exhibited the highest reduce rate of soil available Cd by 32.68％and 28.95％,respectively.These findings provided theoretical basis for selecting soil passivators of heavy metals.
cadmiumadsorptionsoil available cadmiumpassivation
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